For once, I wasn’t able to find something suitable for what I wanted. Annoyingly, almost all the solutions I could find were some variation of ‘make a grid image in photoshop and tile it on an overlay’. While quaint, I wanted something I could easily tweak the baselines on without making several different images. So, my quest resulted in a little script that uses HTML5 canvas drawing and jQuery to build up a baseline grid, a little magic to figure out the baseline and font size, and a button easily switch it on or off for whatever site its put into. I’m considering turning it into a chrome plug in at some point to allow me to use it on any site, but for now you can use it as is.